1. Field of the Invention
The invention relates to a magnetic-tape apparatus comprising a drive arrangement for driving the magnetic tape, which arrangement comprises at least one brake disc which is rotatable in opposite directions of rotation and a block-brake device for braking the brake disc, which device comprises a brake block which is adapted to cooperate frictionally with the brake disc and which is arranged on a first lever, which first lever is pivotally connected to a second lever which is pivotable about a pivot, a coupling means being arranged between the two levers to provide a positive coupling during braking in one direction of rotation of the brake disc, and the two levers being interconnected via a spring means to provide a non-positive coupling during braking in the other direction of rotation of the brake disc.
2. Description of the Prior Art
A magnetic-tape apparatus of the type defined in the opening paragraph is known from DE-AS 1,272,646. In this known apparatus the block-brake device comprises a separate coupling means between the two levers. This separate coupling means is constituted by a limb which is integral with and laterally projects from the second lever and which cooperates with the L-shaped first lever. Thus, the known apparatus requires the use of specially shaped or constructed levers. In addition, the known apparatus comprises a separate spring means arranged between the two levers. This separate spring means is constituted by a tension spring whose ends are attached to the two levers. As is known, such a tension spring exhibits a linear characteristic, i.e. the spring force of a tension spring is in principle directly proportional to the spring excursion, which in its turn depends on geometrical tolerances in the lever system formed by the two levers. However, as a result of this, the spring force and the braking torque, which is dependent on the spring force, depend to a comparatively large extent on geometrical tolerances. Moreover, it is to be noted that the spring force of such a tension spring is subject to substantial tolerances, so that the actual spring force may deviate to a comparatively large extent from a given nominal value, which is also unfavourable in order to obtain a specific desired braking torque.